Referring to FIGS. 1 and 2, description will be given of a conventional technique.
The conventional communication apparatus or device, when adopting a natural air-cooling system because of a small number of transceiver units 2, includes a housing 1, i.e., a natural air-cooling rack 1 in which a branching unit 3, a transceiver unit 2 for natural air-cooling, and a modem/controller unit 5 are installed downward in this order as shown in FIG. 1A. In each transceiver unit 2 in FIG. 1B, heat is radiated from a natural air-cooling radiator 7. If a large number of transceiver units 2 are packed into the conventional apparatus and hence forced air-cooling is employed to cope with high-density mounting of the transceiver units 2. The housing 1 includes a branching unit 3, a transceiver unit 2 for forced air-cooling, and a modem/controller unit 5 that are arranged from the top in this order as shown in FIG. 2A. When a fan unit 4, which is disposed above or below transceiver units 2 shown in FIG. 2B, is activated, heat is radiated from the forced air-cooling radiator 8 of the transceiver unit 2.
As for an example of the conventional technique using natural air-cooling, specifically, a “microwave communication device” that radiates heat by means of radiation fins attached to a housing (for example, Japanese Patent Application Laid-Open No. 2000-13063). Also, there is described an example of the conventional art using forced air-cooling, namely, a “communication device mounting structure and heat radiation method for the same” in which heat is radiated from the device via heat radiation fins while fans suctions air (for example, Japanese Patent Application Laid-Open No. 2004-140015).